VBR MP3 audio broken

[Tristan]

Binary package hint: mplayer

The mplayer package for Ubuntu is broken when playing VBR MP3 audio in various
video files (mpeg4 part 2 and part 10, MPEG compliant and incompliant frame
order, AVI, mp4, mkv, etc). I've origially reponded to a seemingly ignored bug
(bug #163382), so I'm posting a new bug with more information and specific to
resoloving this issue.

The bug is libmad cannot playback VBR MP3 correctly. The video will sound
alright, but the video will quickly get out of sync! This is a known bug with
the mplayer developers. See:

http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2008-January/055849.html
http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2006-August/045241.html

Considering the age of this known bug and the unwillingness to fix the
decoder, libmad should not be the default decoder for video playback. There
are two good reasons for this. First, 21% of my video files that use MP3 audio
are VBR, so a fith the time my files fail to play correctly. Second, libmad is
no longer maintained. The last release was in 2004, and some discussion via
IRC has produced some clear issues with parts of the libmad code. As a
specific example, mad doesn't correctly parse info tags.

My recommendation is to switch to the official mp3lib decoder or the ffmpeg
decoder. Unfortunally, neither these are a good choice. Bug #85751 details a
bug in mp3lib for mplayer 1.0 rc1. Comments in that bug and bug #52729 further
detail issues with ffmpeg's decoder. If mp3lib has been fixed in 1.0 rc2, then
I recommend mp3lib as the default decoder.

mp3lib seems to have been fixed upstream and ffmpeg's decoder has had
multiple fixes checked in since the reported problems. I'll be aiming to
repoduce the original noise bugs. If I can, I'll backport any fixes from upstream
to Ubuntu's stable release.

Related bugs: bug #52729 bug #85751 bug #111025 bug #163382

[Thomas Hotz (thotz-deactivatedaccount)]

Can't reproduce this on Ubuntu 13.04. What Ubuntu version and mplayer version do you use now? Thank you for telling us!

[Tristan (tristan-willy)]

Thanks for the check, Thomas. I plan on upgrading to Ubuntu 13.04 soon
and I'll give this bug report another shot at reproducing.

On Sun, Apr 28, 2013 at 1:31 AM, Thomas Hotz <email address hidden> wrote:
> Can't reproduce this on Ubuntu 13.04. What Ubuntu version and mplayer
> version do you use now? Thank you for telling us!
>
> ** Changed in: mplayer (Ubuntu)
> Status: New => Incomplete
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/244722
>
> Title:
> VBR MP3 audio broken
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/mplayer/+bug/244722/+subscriptions

--
- Tristan

[Tristan (tristan-willy)]

The original complaint is that libmad causes sync issues with VBR MP3 and that Ubuntu used libmad by default for its mplayer package. I just upgraded to 13.04 and it appears that libmad is not the default anymore (ffmpeg is used instead). I installed libmad and tried to force mplayer to use it (-ac mad) and I got:

Forced audio codec: mad
Requested audio codec family [mad] (afm=libmad) not available.
Enable it at compilation.

Since libmad is no longer compiled with Ubuntu's mplayer, this bug is fixed.